Spark advance indicator



Nov. 25, 1941. K. R. ELDREDGE 2,263,859 7 SPARK ADVANCE INDICATOR Filed March 23, 1940 4.6 o/szw/auroe [/VVE/VTOR Keane/b A. f/areo e F .2 & g 5 1:9 Arrwmsy Patented Nov. 25, 1941 SPARK ADVANCE INDICATOR Kenneth R. Eldredge, Berkeley, Calif., assignor to Standard Oil Company of California, San Francisco, Calii'., a corporation of Delaware Application March 23,1940, Serial No. 325,584

6 Claims.

This invention relates to a method for measuring and indicating the ratio of intervals between cyclically repeated sets of impulses, and particularly refers to a spark advance indicatdr for a spark ignition internal combustion engine, said indicator adapted to measure the relation between the operation of the ignition system and a predetermined reference point or event in the operating cycle of the engine.

This invention is an improvement on the apparatus shown in my copending joint application with J ohnR. MacGregor Serial No. 141,735, filed May 10, 1937, which issued/January 7, 1941, as Patent No. 2,228,032.

The apparatus of this invention is used to in: dicate the relation between a given point in the cycle of an internal combustion engine, such as top dead center of a piston or a pair of pistons, and the time of the spark ignition of a combustible charge in one or more cylinders. The spark causing the ignition ordinarily precedes the top dead center of the piston by several-degrees, the numerical value of which is known as the spark advance of the engine. Engine designers have appreciated the importance of varying the spark advance to accommodate changes in the engine speed and load. This is accomplished in modern automobiles by incorporating in their spark advance control mechanism a means for increasing the spark advance as theengine speed increases and a means for decreasing that advance at high engine loads. Since mechanical friction or wear may ailfect the action exerted by either, or both, of these control mechanisms, it is apparent that the normal operation of such an engine may be at considerable variance from its designed and most efiicient characteristics.

In the comparison of diflerent types of fuels to determine the effect of antiknock agents and the like, a knowledge of the behavior of the spark ad- 'vance control mechanism is of the utmost importance. Previous to our inventions, it was usually necessary to remove the entire ignition system from a test automobile and to install special equipment in order to ascertain the spark advance-speed-engine load characteristics, and the measurement of these characteristics was so uncertain that accurate comparisons of fuels possibility of the occurrence of for connecting the meter to the current source, and a second current control means which could be a vacuum type discharge tube responsive to the momentary electric potential induced in an electromagnetic pick-up coil spaced from a moving part of the engine, for example, a magnetic armature carried by the flywheel, the induced potential set up in the coil by the passage of the armature acting upon the second tube to disconnect the meter from its current source. The average current measured by the meter thus gave an indication of the ratio of the time during which the current flowed to the time when the current did not flow. Since the starting and stopping of the current were controlled by an ignition system potential and by a predetermined point on the moving crankshaft or flywheel oi the engine, changes in the relationship of these two events would be indicated by .the meter reading.

One of the disadvantages of the apparatus Just described was itssus'ceptibility to stray potentials in the ignition system, it being well known that secondary voltages are induced back into the primary sideof such a system, these stray potentials sometimes actuating the current control means to give faulty or misleading indications. My improved arrangement; which is the subject of this,

application, includes 'a second current control means, ordinarily including a pick-up unit which is angularly spaced from the first unit and is utilized to place that current control means which is responsive to ignition potential in an inoperative condition except during a predetermined part of the cycle of operation, this interval being v chosen to be short enough so that there is no stray ignition system potentials.

It is an object of this invention to provide an improved spark advance indicator mechanism which may be controlled to give an indication of the behavior of a single cylinder or a selected group of' cylinders in a multicylinder engine withtube responsive to an ignition system potential out interference from the ignition system potentials acting upon othercylinders in the engine.

Another object is to provide an apparatus for accurately determining the interval ratio between cyclically repeated sets of impulses, regardless of the nature of the impulses, so long as they may be utilized to start and stop the flow of an electric current.

Another object is to provide an apparatus for accurately determining the spark advance of a multicylinder internal combustion engine without requiring extensive mechanical alterations to the engine structure, which apparatus is simpleand of conductor 3|.

These and other objects and advantages will be further apparent from the following description and from the accompanying drawing which forms a part of this specification and illustrates the essential features of the invention as applied to a spark advance indicator.

In the drawing: Figure l is a diagrammatic end elevation view of this apparatus as applied to a multicylinder engine, together with a schematic connection diagram of a current-controlling and metering means.

Figure 2 is a section on line II--II of Figure 1 showing a preferred form of electromagnetic pick-up unit and an actuating means therefor.

In the drawing, reference numeral I designates a multi-cylinder spark ignition type of internal combustion engine provided with an electric ignition system distributor, generally desigv.nated II, and a flywheel or other exposed rotating part I2 which is in synchronism with the crankshaft of the engine. In this example, an iron or steel armature I3 is secured to flywheel I2 and is adapted successively to pass close to the pole-pieces of a first electromagnetic pick-up unit I4 and a second pick-up unit I5. The voltage impulses caused by the passage of armature I3 close to the pole-pieces of the pick-up units and voltage impulses from the primary or the secondary circuit of the ignition system represented by distributor II are utilized to control the average flow of electric current through a meter I6 which may be calibrated directly in degrees of spark advance, as will be descisibed below.

The control apparatus used for this purpose consists of a first gas or vapor-filled grid-controlled discharge tube I! having a control grid I8, an anode or plate I9, and a cathode or filament 2!]. Cathode may be energized by any suitable source, of electric current not shown. The anode or'plate potential for tube I1 is supplied from battery 2| through conductor 22 and series resistors 23 and 24. The control grid I8 of tube I1 is connected by means of conductor 48 to either the primary or the secondary circuit in the ignition system distributor II and is adapted to fire tube I1 and cause it to conduct current from. battery 2| through meter I6 when a suitable voltage impulse is impressed upon grid I8 from the ignition system if an adequate potential exists on the anode or plate I9. In the meter circuit resistors 23 and 24 limit the meter current to a value which gives the desired deflection on the meter scale.

In order to prevent tube I! from being fired by any but the desired electric potentials from the distributor I I, and also to terminate the current flow through meter I6 at a predetermined point in the rotation of flywheel I2, a second gas or vapor-filled grid-controlled discharge tube 25 is provided, this tube having a control grid 26, an anode 21 and a cathode 28, as shown in Figure 1. Control grid 26 of tube 25 is connected by means of conductor 29 to the second pick-up unit I5 mentioned above. The function of tube 25 is to extinguish tube I! and terminate the current flow through meter I6. This is accomplished by connecting the anode 21 of tube 25 to the intermediate point 30 between resistors 23 and 24 by means Tubes I1 and 25 require substanitally equal potentials upon their respective anodes, but tube 25 has upon its anode a higher potential than that which exists upon the anode ,of tube I1 because of the potential drop through resistor 24. Consequently, when tube 25 is fired by the passage of armature I3 across the polepiece of pick-up unit I5 the anode potential available for tube I1 falls below that which is necessary to render tube II conducting. Thereafter, gas-filled tube 25, because of its well known characteristics, remains conducting even though the momentary electric potential on its control grid 25 is terminated, and prevents tube II from being fired by subsequent undesired potentials from the ignition system distributor II.

A third tube 32 is used to place the first tube II incondition to become conducting as soon as another desired potential impulse is received from distributor I I. Tube 32 is of the vacuum type and is provided with a control grid 33, an anode 34 and a cathode 35. Grid 33 of tube 32 is connected by means of conductor 36 to the first pickup unit I4. The anode 34 of tube 32 is connected by means of conductor 31 to the anode circuits of tubes I1 and 25 at intermediate point 30 so that anode 34 is in parallel with anode 21 of tube 25.

' As soon as flywheel I2 has completed the desired portion of its rotation and is approaching the point after which a desired $r predetermined potential impulse from distributor II is to be impressed upon control grid I8 of the first tube II, armature I3 passes pick-up unit I4 and induces therein a potential impulse which is impressed upon'control grid 33 of vacuum tube 32. This causes tube 32 momentarily to become conducting, thereby reducing the anode potential of tube 25 and extinguishing the latter. This operation places tube II in condition to be controlled by its own grid I8 by restoring its anode potential and a subsequent potential impulse from the distributor II again starts a current flow through meter I6. Shortly thereafter armature I3 induces a potential in pick-up coil I5, firing tube 25 which extinguishes tube I! in the manner previously described and keeps that tube extinguished until tube 32 is again fired by the first pick-up unit I4. This cycle of operation is repeated and is effective to control the average current flowing through meter I6 so that it will truly represent the ratio of the interval between the desired or predetermined ignition systern potential impulse and the passage of armature I3 across pick-up unit I5, the position of the latter being easily related to any desired point in the cycle of the operation of the engine, such as the top center position of one or more of the pistons in engine III, to the interval represented by the remaining portion of the rotation of flywheel I2.

Figure 2 illustrates a preferred form of construction for the electromagnetic pick-up units I4 and I5. Armature I3, which is desirably of paramagnetic material such as steel or soft iron, is secured to the face of flywheel I2 by means of a machine screw 38 so as to extend outwardly at right angles to the plate of rotation of flywheel I2. The pick-up unit proper consists of a cylindrical body 39 of steel or other paramagnetic material recessed to receive a winding 40 supported by an insulating spool 4|. The pole-piece -42 of the pick-up unit is desirably a small which may be a short metal tube 44 fitted with an insulated central contact 45 and provided with threads 46 to which a screw-type connector may be secured. Pick-up units l4 and I are desirably supported by means of a frame 41 adjustably positioned with respect to flywheel [2 so that the armature I3 is in proper relationship to the outer end of pole-pieces 42. Usually pick-up unit I4 is set on frame 41 to be actuated by armature l3 at a point about 60 before the top center position of the piston in the cylinder in which will occur the spark used to start the'current flow through meter 16. The exact position is not at all important. The location of the second pick-up unit I5 is necessarily chosen so that armature I3 passes the pole-piece 42 of that unit after the occurrence of the spark which has caused tube I! to become conducting and start a current fiow through meter Hi.

In addition to its application to the spark advance indicator described and claimed in my copending joint application Serial No. 141,735 with John R. MacGregor, now Patent No. 2,228,032, it is obvious that the interlocking arrangement of tubes I l, and 32 could be used wherever cyclically repeated impulses are to be selectively utilized to control a current flow. It is believed that this invention comprehends broadly a device for measuring the ratio of intervals between -two predetermined impulses in a series of repetitive or cyclically repeated impulses, the time of occurrence of the two predetermined impulses being variable by some outside factor. A preferred means for doing this may comprise a first means responsive to the first of said predetermined impulses, said means being efiective to initiate a flow of electric current through a current averaging meter, a second means responsive to the second of said predetermined impulses adapted to terminate the current fiow through said meter and also to render said first-named means unresponsive to succeeding impulses, and a third means actuated by a thirdepredetermined impulse taking place just before a second occurrence of said first predetermined impulse for rendering the first-named current control means responsive to one succeeding impulse. In this example-gridcontrolled electron or discharge tubes are used for the three means just named, the anodes of.

the first and second of these tubes being supplied from a common source of ionizing potential, and the anode of the third tube being supplied by a lower potential from said same source.

Although a specific embodiment of this invention has been described and illustrated, it is understood that many changes and modifications could be made and all those that are within the scope of the following claims are embraced thereby.

I claim:

1. A spark advance indicator circuit for a multicylinder spark ignition internal combustion engine comprising an electric current meter. a source of electric current for said meter. 21 first electric current control means adapted to be connected to the ignition system of said engine to receive a succession of electrical impulses therefrom any one of which is adapted to actuate said control means to connect said current meter to said current source, a second electric current control means connected to said first control means and responsive to a predetermined first position of a cyclically moving part of said engine to actuate said first current control means to disconnect said meter from said current source and to render said first current control means unresponsive to subsequent ignition system potentials, and a third current control means connected to said first current control means and responsive to a second position of said cyclically moving 7 part of said engine to render said first current control means responsive to a succeeding ignition system electrical impulse.

2. A spark advance indicator according to claim 1, in which said electric current control means comprises grid-controlled discharge tubes.

3. A spark advance indicator according to 'claim 1, in which said electric current control means comprises grid-controlled discharge tubes, said second and third named current control means each comprise an electromagnetic pick-up unit, and said cyclically moving part of said engine comprises an armature of paramagnetic material adapted to induce a potential in each of said pick-up units to actuate their respective current control means.

4. A sparkadvance indicator according to claim 1, in which said second and third electric current control means each comprise an electromagnetic pick-up unit, and said cyclically moving part of said engine comprises an armature of paramagnetic material secured to the fiywheel of -said engine and adapted to induce a potential in each of said pick-up units.

5. A spark advance indicator for a multi- 2 cylinder spark ignition internal combustion engine comprising a first means responsive to a cyclically moving part of said engine to produce an electric current impulse at a predetermined point in the travel of said moving part, a second be actuated by any one of a succession of spark I producing potentials therein, the second adapted to be connected to said first named electric current impulse producing means to be actuated by i a current impulse therefrom and connected to said first electric current controller to render it inoperative, and the third controller adapted to be connected to said second named electric currentimpulse producing means to be actuated by acurrent impulse therefrom and connected to said first electric current controller to render it responsive to a succeeding spark producing potential from said ignition system.

6. A spark advance indicator for a multicylinder spark ignition internal combustion engine comprising a first magnetic pick-up. coil adapted to be spaced from a cyclically moving part of said engine and to have induced therein an electric potential by the motion of said moving part-a second magnetic pick-up coil spaced from said first coil and similarly responsive to the induction of electric potentials by the motion of first controller to cause the latter to be unresponsive to spark producing potentials after a potential has been induced in said first pick-up coil, and the third controller connected to said second magnetic pick-up coil and to said first electric controller so constructed and arranged that an induced potential in said second pick-up coil will actuate said third controller to place said first controller in condition to be responsive to a suceeding spark producing potential from 10 said ignition system.

KENNETH R. EIDREDGE. 

